SEOUL, Oct. 12 (Yonhap) -- Opposition presidential candidate Moon Jae-in vowed Friday to safeguard the country's western maritime border with North Korea while at the same time seeking detente with the communist neighbor.

The remark came amid allegations that late President Roh Moo-hyun, whom Moon served as chief of staff, said during his 2007 summit with then North Korean leader Kim Jong-il that the South would not insist on the Yellow Sea border that Pyongyang has disputed.

Moon and other officials of the previous administration have rejected the allegations.

"I will ensure a firm defense capability that will not a allow a single provocation from North Korea in the Yellow Sea," Moon said during a meeting with former defense ministers and retired generals at the Airforce Club in Seoul.

"Based on that defense capability, I will end military confrontation in the Yellow Sea and actively pursue dialogue toward peace," he said. Moon, the 59-year-old candidate of the main opposition Democratic United Party (DUP), also claimed the current administration of President Lee Myung-bak had failed completely in national security as a total of 50 South Koreans were killed in two North Korean attacks in 2010 on its watch.

National security is a key political issue ahead of December's presidential election as the two Koreas remain in a technical state of war following the 1950-53 Korean War that ended in an armistice, not a peace treaty.

North Korea has never recognized the sea border, known as the Northern Limit Line (NLL), which was drawn unilaterally by the U.S.-led United Nations Command at the end of the Korean War. The communist nation demands the maritime border be moved further south.

"(The 2003-2008 Roh administration) held military talks with North Korea and established a system to prevent skirmishes in the Yellow Sea," Moon said. "During those five years, there wasn't a single military clash not only along the NLL but also along the (inter-Korean land border)."

By contrast, the Lee administration's "national security incompetence" led to the sinking of the Cheonan warship in March 2010 and an artillery attack on the border island of Yeonpyeong in November of the same year, Moon claimed.

In a five-point national security plan including the defense of the NLL, Moon said he would establish a security environment in which the public feels safe, as well as push for a smooth planned transition of wartime operational control from U.S. to South Korean command in 2015, and a gradual reduction of military troops and mandatory military service.